This invention relates to a wheel support apparatus in which a hub shaft of a hub wheel for the mounting of a wheel thereon and an outer ring of a constant velocity joint are connected together in a torque-transmitting manner.
There is known one conventional wheel support apparatus of this type in which a hub shaft of a hub wheel and an outer ring of a constant velocity joint are interconnected by an connecting bolt, and also two side surface splines are formed respectively on an end surface of the hub shaft of the hub wheel and an end surface of a side wall portion of the constant velocity joint which abuts against the end surface of the hub shaft, and the hub wheel and the constant velocity joint are connected together in a torque-transmitting manner through the two side surface splines (see, for example, JP-A-63-184501).
When the two side surface splines formed respectively on the end surface of the hub shaft of the hub wheel and the end surface of the side wall portion of the constant velocity joint are meshed with each other, thereby connecting the hub wheel and the constant velocity joint together in a torque-transmitting manner as described above, it is feared that muddy water or the like splashed up by a wheel may accidentally intrude into the interior through a clearance between the two side surface splines meshed with each other, so that rust may develop in the interior.
One conventional wheel support apparatus of the type described is disclosed, for example, in JP-A-2002-114004.
In this wheel support apparatus, a double row angular contact ball bearing 120 comprising an inner ring 121, an outer ring 130 and balls (rolling elements) 141 and 142 is mounted on an outer peripheral surface of a hub shaft 113 of a hub wheel 110 as shown in FIG. 17.
On the other hand, a connecting shaft portion 163 is formed integrally on and extending from an end surface of a side wall portion 161 of an outer ring 160 of a constant velocity joint 150 to which an end portion of a drive shaft 151 is connected. An internal spline 114 is formed on an inner peripheral surface of a bore of the hub shaft 113 of the hub wheel 110, and an external spline 164 for meshing with the internal spline 114 is formed on an outer peripheral surface of the connecting shaft portion 163.
The connecting shaft portion 163 is inserted and fitted into the bore of the hub shaft 113 of the hub wheel 110 while the internal and external splines 114 and 164 are brought into meshing engagement with each other, and then a lock nut 166 is fastened onto an male-threaded portion 165 projecting from a distal end of the connecting shaft portion 163, and by doing so, the hub wheel 110 and the constant velocity joint 150 are connected together in a torque-transmitting manner.
In the wheel support apparatus disclosed in JP-A-2002-114004, for example, during the travel of a vehicle, a torque of the outer ring 160 of the constant velocity joint 150 rotating in the same direction as the direction of rotation of the drive shaft 151 is transmitted to the hub wheel 110 through the internal and external splines 114 and 164 meshing with each other, thereby driving the wheel to rotate it.
At this time, a relative slip (slip including a torsion) sometimes develops between the end surface of the side wall portion 161 of the outer ring 160 of the constant velocity joint 150 and an end surface (that is, an end surface of a caulked portion 117) of the hub shaft 113 of the hub wheel 110, so that an abnormal sound is generated.
In order to prevent the generation of an abnormal sound due to a relative slip between the end surface of the side wall portion 161 of the outer ring 160 of the constant velocity joint 150 and the end surface of the hub shaft 113 of the hub wheel 110, the Applicant of the present invention has proposed a structure as shown in FIG. 18, in which a side surface spline 280 is formed on an end surface of a caulked portion 217 of a hub shaft 213, and a side surface spline 290 is formed on an end surface of a side wall portion 261 of an outer ring 260 of a constant velocity joint 250 abutting against the end surface of the hub shaft 213, and the two side surface splines 280 and 290 are meshed with each other to connect the hub shaft 213 of a hub wheel 210 and the outer ring 260 of the constant velocity joint 250 together in a torque-transmitting manner.
In the case where the side surface splines 280 and 290 are formed respectively on the end surface of the caulked portion 217 of the hub shaft 213 and the end surface of the side wall portion 261 of the outer ring 260 of the constant velocity joint 260 by forging, each bottom land 282, 292 of each of the two side surface splines 280 and 290 is formed into an inclined surface gradually increasing in depth from its radially-inner end to its radially-outer end.
Therefore, the meshing engagement of the two side surface splines 280 and 290 is limited at the radially-inner portions of the bottom lands 282 and 292. As a result, non-contact portions S where the spline teeth of the spline 280 and the spline teeth of the spline 290 will not contact each other develop at the radially-outer end portions of the bottom lands 282 and 292 of the two side surface splines 280 and 290. Therefore, it is thought that a contact pressure and a shear stress of tooth flanks of the spline teeth at the mutually-contacting portions of the two side surface splines 280 and 290 increase, so that the durability may be adversely affected.
Another conventional wheel support bearing apparatus of this type is disclosed in JP-A-57-178903.
In this conventional wheel support bearing apparatus, in order to connect a hub wheel 210 and a constant velocity joint 250 together in a torque-transmitting manner as shown in FIG. 19, a side spline (side surface spline) 290 is formed on an end surface of a hub shaft 213 of the hub wheel 210, and a side spline (side surface spline) 280 is formed on an end surface of an end wall portion 261 of the outer ring 260 of the constant velocity joint 250, and the hub wheel 210 and the constant velocity joint 250 are connected together in a torque-transmitting manner through the two side splines 280 and 290 meshing with each other.
In order to interconnect the hub shaft 213 of the hub wheel 210 and the outer ring 260 of the constant velocity joint 250, an internally-thread portion 263 corresponding to an male-threaded portion 273 of an connecting bolt 270 is formed in the end wall portion 261 of the outer ring 260 of the constant velocity joint 250, while a center hole 214 for the passage of a shank 272 of the connecting bolt 270 therethrough is formed through a center portion of the hub shaft 213.
The two side splines 280 and 290 are meshed with each other, and in this condition the shank 272 of the connecting bolt 270 is passed through the center hole 214 of the hub shaft 213 from the outside thereof, and the male-threaded portion 273 on this shank 272 is threaded into the internally-threaded portion 263 of the end wall portion 261 of the outer ring 260 to be fastened thereto, thereby coupling the hub shaft 213 of the hub wheel 210 and the outer ring 260 of the constant velocity joint 250 together.
Each tooth top 283 of the side spline 280 on the end wall portion 261 of the outer ring 260 of the constant velocity joint 250, as well as each bottom land 292 of the side spline 290 on the hub shaft 213, is disposed in a pane (vertical plane) perpendicular to a center axis of the hub shaft 213.
In the condition in which the hub shaft 213 of the hub wheel 210 and the outer ring 260 of the constant velocity joint 250 are connected together by tightening the connecting bolt 270, each tooth top 283 of the side spline 280 contacts the corresponding bottom land 292 of the side spline 290. Also, each bottom land 282 of the side spline 280 of the constant velocity joint 250 and a corresponding tooth top 293 of the side spline 290 of the hub shaft 213 are disposed out of contact with each other, with a clearance S′ formed therebetween.
In the wheel support bearing apparatus disclosed in JP-A-57-178903, it is rather difficult to interconnect the hub shaft 213 of the hub wheel 210 and the outer ring 260 of the constant velocity joint 250 in aligned relation to each other (that is, with their center axes coinciding with each other), with the two side splines 280 and 290 meshing with each other, by tightening the connecting bolt 270, and it is thought that the hub shaft 213 of the hub wheel 210 and the outer ring 260 of the constant velocity joint 250 can be brought out of alignment with each other (that is, their center axes become misaligned with each other). This misalignment causes vibration and an abnormal sound.